1. Field of the Invention
The present invention relates to the field of medical devices and, more particularly, to an expandable inter vivos tube.
2. Background of the Invention
Inter vivos tubes, such as endotracheal tubes, are used to provide gases to the lungs during surgery. For example, an endotracheal tube is inserted into the trachea with its distal tip advanced halfway toward the tracheal bifurcation to provide gases, such as oxygen and anesthetics to a patient, during surgery. The exposed portion of the endotracheal tube is then firmly taped to the patient's face to prevent undesirable movement.
To align the position of conventional endotracheal tubes, an inflatable cuff balloon, at the distal end of the endotracheal tube, is inflated to correspond to the inner diameter of a portion of the trachea, thereby centering, or otherwise positioning, the endotracheal tube within the trachea. The cuff balloon, however, does not completely obstruct the entire trachea; only the portion where it is anchored is obstructed. When the cuff balloon is inflated, confirmation of the expanded balloon's contact within the trachea is achieved and delivery of anesthetic gases is performed.
Because of various sized endotracheal tubes, it is preferable to at least make the outer diameter of the endotracheal tube closely proximate to the size of the glottis, or opening between the vocal cords, for selective positioning of the endotracheal tube at a predetermined dilation. Therefore, various sized tubes are used, and the anesthesiologist or nurse anesthetist must choose from a variety of sized tubes to insert in the patient. If nasotracheal intubation or tracheostomy tubes are required in present practice even smaller interior diameters (ID) tubes are used.
Conventional endotracheal tubes vary in size and are numbered according to an internal diameter (ID). For example, for children, tubes are measured at about 3.5 to 7 mm (millimeters) internal diameter and from 7 to 11 mm for an adult. The internal diameter in women varies in general from 7.0 to 8.5 mm ID and in men from 8 to 10 mm ID. Typically, an endotracheal tube size selected for each patient is empirically selected by the anesthesiologist based on the patient's gender, age and size.
Ideally, the endotracheal tube should approximate as closely as possible the glottic size of the patient. Since there is no way to estimate the glottic size prior to the administration of anesthesia, in the existing prior art endotracheal tubes, a distal inflatable cuff is incorporated into the present day endotracheal tube which, when inflated, compresses the tracheal wall, thus creating a closed circuit between the endotracheal tube inflow from the anesthesia machine and outflow from the patient's lung to the exhalation valve. When nasotracheal intubation or tracheostomies is necessary, the internal diameter of the endotracheal tube is even less than the normal size, which is selected for orotracheal intubation, even greater respiratory resistance is created.
As noted in “Clinical Anesthesia,” 1989 Edition, J. B. Lippincott Company, edited by Paul Barash, MD, Bruce Cullen, MD, and Robert Stoelting, MD, “[e]ndotracheal tube resistance varies inversely with the tube size. Each millimeter decrease in tube size is associated with an increase in resistance of 25 to 100%. The work of breathing parallels changes in resistance. A one (1) mm decrease in tube size increases the work of breathing from 34 to 154%, depending on the ventilatory pattern”.
Therefore, in existing prior art inter vivos tubes, the internal diameter is small, and the only large portion is the external cuff balloon. This makes it harder for a surgical patient to breathe through the small internal diameter of the existing endotracheal tubes, especially if the patient must breathe spontaneously without assistance.
In summary, the prior art uses a local, inflatable balloon at the distal portion of an endotracheal tube, which narrows the patient's air way at the vocal cord level and may damage the vocal chords of the patient, if not property installed.
Applicant's prior U.S. Pat. No. 3,968,800 dated Jul. 13, 1976 and U.S. Pat. No. 4,827,925 dated May 9, 1989 describe an adjustable endotracheal tube which is complex to expand, and which does not have flexibility in being adapted to varying sized tracheas of different patients. Applicant's other prior U.S. Pat. No. 4,722,335, dated Feb. 2, 1988, discloses an expandable endotracheal tube including two overlapping curved segments, which when joined together form a closed tube. Similarly, applicant's prior U.S. Pat. No. 5,647,358, dated Jul. 15, 1997, discloses an expandable inter vivos tube that provides for expansion of the tube along at least designated parts of the tube. However, the configuration may be conceptually possible but in practical terms, difficult to construct and maintain at present prices.
Hence, there is a need in the industry for an expandable inter vivos tube that is easy to construct, easy to install, expand and remove during a procedure while reducing construction and costs of construction.